1. Field of the Invention
The present invention relates to a locking device capable of holding a seat back of a vehicle seat at a predetermined rising angle.
2. Description of the Related Art
This type of locking device for a seat back is disclosed in Japanese Patent No. 3810944.
The locking device for a seat back, which is disclosed in Japanese Patent No. 3810944, urges a lock pin provided on a base plate which is fixed to the seat back by means of a spring, engages the lock pin with one of the lock holes bored on a lock plate fixed to a vehicle body, and thereby holds the seat back at a predetermined rising angle. Onto the base plate, a lift lever having two arm portions is pivotally attached. This lift lever is held at an initial position by an urging force of the spring. Meanwhile, in the lock plate, a guide hole is formed, into which one of such arms of the lift lever can enter when the seat back is held at a rising position. At the time of rising rotation of the seat back, one of the arm portions of the lift lever is popped up by a front end edge of the guide hole of the lock plate, and the lift lever is rotated positively (rotated backward) from the initial position. When one of the arms is rotated positively from the initial position as described above, the other arm portion moves the lock pin in a release direction, whereby the lock pin is lifted up above the base plate. In such a way, the lock pin is prevented from colliding with the base plate. Then, at the time of getting over the front end edge of the lock plate, one of the arms of the lift lever is rotated reversely (rotated forward) by the urging force of the spring, and enters into the guide hole. Then, the lock pin is urged downward by the urging force of the spring, whereby the lock pin enters into the lock hole, and is engaged with the lock hole concerned. In such a way, the seat back is held at a predetermined rising position.
In accordance with the locking device as described above, at the time of the rising rotation of the seat back, one of the arms of the lift lever and the front end edge of the guide hole of the lock plate play roles of sensors, whereby the lock pin is smoothly locked without colliding with the lock plate.